1. Field of the Invention
The present invention relates to a feeding unit for metallic linear material applicable to a continuous manufacturing apparatus for fastener stringer which intermittently feeds an engaging element metallic linear material for a slide fastener to an engaging element implanting section, the metallic linear material having a substantially Y-shaped section molded preliminarily by rolling.
2. Description of the Related Art
As for this kind of slide fastener engaging element, a long metallic linear material having a circular section is formed into a substantially Y shape in its lateral section through a plurality of mill rolls, and is intermittently fed by an amount corresponding to a single engaging element and successively cut out into a predetermined thickness by a cutting punch and a cutting die to obtain an engaging element material. By molding its engaging head into a mountain like shape by a forming punch and a forming die, an engaging element (hereinafter referred to as a linear engaging element) is molded. Usually, the cutting punch is fixed to a part of the machine frame, and the cutting die and forming die are integrated with a ram, and at the time of retraction, cut out a linear material with the cutting punch. Then, the forming punch is actuated to mold the linear material into a mountain like shape at its retraction stop end. Thereafter, the ram advances toward an engaging element attaching portion of a fastener tape, and a pressurizing punch is actuated at its advancement stop end position, so that right and left leg portions of the engaging element are pressurized and attached to the engaging element attaching portion of the fastener tape. After the engaging element is attached to the fastener tape, an intermittent feeding portion is actuated so as to intermittently feed the fastener tape by an equal pitch. Such a molding method for a linear engaging element has been disclosed in, for example, Japanese Patent Publication No. 59-51813.
FIG. 5 of patent document 1 shows a schematic configuration of a linear material feeding unit for intermittently feeding the metallic linear material by an amount corresponding to a single engaging element. A conventional linear material feeding unit intermittently rotates a ratchet wheel by a ratchet pawl provided at a front end of a cam driven mechanism which is reciprocated by a rotation of a cam provided on a main shaft. A rotation of the ratchet wheel is transmitted to a drive roller of the linear material feeding unit which shares a supporting shaft with the ratchet wheel, so that the metallic linear material is nipped by a pair of rollers comprising the drive roller and a driven roller and is intermittently fed synchronously with attachment of the engaging element. At this time, if an interval between the drive roller and the driven roller is set up, the interval is unchanged.
The above-mentioned metallic linear material has a substantially Y-shaped section comprising a head portion for forming a head of an engaging element and leg portions for forming right and left leg portions of the engaging element. Thus, a continuous convex row is provided along the peripheral face of the drive roller, and a concave groove is provided along the peripheral face of the driven roller. On the other hand, because the metallic linear material has an irregular shaped section, the metallic linear material may be fed in a twisted state although slightly by the time when it reaches the drive roller. When the metallic linear material is fed from between the drive roller and the driven roller, the metallic linear material is nipped between the convex row of the drive roller and the concave groove of the driven roller such that the convex row of the drive roller is fitted to between the right and left leg portions of the metallic linear material while the concave groove in the driven roller is fitted to the head portion of the metallic linear material.
A contact pressure applied to the metallic linear material between the rollers needs to be increased in order to feed the metallic linear material having such an irregular shaped section securely without any slippage by nipping with the pair of the drive roller and driven roller. On the other hand, both the sectional areas of the head portion and the right and left leg portions of the metallic linear material having the irregular shaped section are small, and the linear material is often fed in a twisted state, though it is slight, by the time when it reaches the drive roller and the driven roller. Even if the linear material is introduced into between the rollers in such a twisted state, the metallic linear material is caught between the rotating rollers in the twisted state, so that the metallic linear material is damaged seriously.
Further, the metallic linear material having the irregular shaped section is likely to slip out of fitting between the drive roller and the driven roller with acceleration of manufacturing speed. If the metallic linear material slips out of the fitting condition, it cannot return to its original fitting condition easily, so that the sectional shape of the metallic linear material is deformed. Also, as described above, if the metallic linear material is caught between a drive roller and a contact roller, an excessive load is applied to the drive roller, thereby finally stopping the rotation. At this time, not only the metallic linear material is damaged, but also the ratchet wheel or ratchet pawl which rotates the drive roller is damaged.
It can be considered to elastically urge the driven roller to the drive roller in order to eliminate such an inconvenience. However, according to such a conventional method of feeding the metallic linear material with the drive roller and drive roller in one pair, the contact pressure of each roller with respect to the metallic linear material needs to be set high in order to exclude the aforementioned slippage. When the metallic linear material is caught between both the rollers, the driven roller cannot move against a strong elastic force, thereby still damaging the metallic linear material and the ratchet wheel and the like. If only the pair of the drive roller and driven roller is provided, when a metallic linear material slips out of the rollers, a track of the slipped linear material changes. Thus, the linear material cannot return to its original nipping condition, thereby causing the same inconvenience as described above.
The present invention has been achieved to solve such a problem, and an object of the invention is to provide a feeding unit for metallic linear material applicable for a continuous manufacturing apparatus for a fastener stringer, the feeding unit protects the metallic linear material from slipping out of feeding rollers easily, and even if the linear material slips out for a while, returns it to its original track immediately, thereby feeding the metallic linear material securely despite its irregular shaped section without damaging the linear material or ratchet wheel.